This invention relates to an assembly line for manufacturing electronic assemblies such as printed circuit boards containing discrete components. The invention is particularly useful for, but not necessarily limited to, maximizing the utilization of the assembly line while at the same time providing maximum flexibility in product mix and volume.
In production assembly lines used for mounting electronic components to circuit boards, the circuit boards are generally conveyed through the assembly line on conveyors. Various assembly processes such as solder stenciling, component mounting and reflow soldering are typically performed. Typically, the conveyors are parallel tracks that carry the circuit board through the various stages of assembly, from one station to another. During conveying it is common practice to support the circuit boards along the edges and maintain them in a substantially horizontal plane and isolated from vibration so that the possibility of component misalignment is reduced.
In conventional systems, the assembly line is usually optimized to enable high efficiency and throughput. This is because of the substantial capital. cost of the highly sophisticated and automated equipment employed in modern circuit board assembly lines. A typical line costs two million dollars, and some are as high as ten million dollars. Obviously, one is desirous of operating at highest efficiency in order to realize maximum return on the dollars invested in the equipment, and assembly lines are typically dedicated to a single product so that down time required to reconfigure the assembly line is minimized.
On the other hand, the demands of the modern marketplace are such that it is desirous to produce a variety of products in order to satisfy the increasing appetite for electronics that provide features that are tailored to the individual consumer. This means that either several dedicated lines must be employed, or the line must be frequently reconfigured. In the first case, the capital cost for additional lines is high, and additional engineering overhead must be provided in order to keep these sophisticated lines running-smoothly. In the second instance, reconfiguring the line requires that the line be stopped and reconfigured. Even with today""s formidable computing power, downloading new programs consumes precious time and decreases the utilization of the assembly line. Utilization is the converse of flexibility, and thus, the manufacturer is forced to choose from two mutually exclusive goals, high flexibility or high utilization. The industry has struggled in vain for many years in attempts to find a solution to this dilemma. To date, all prior art solutions have been a compromise, sacrificing one goal in pursuit of the other. The ability to have maximum utilization and maximum flexibility on the same assembly line would be a valuable addition to the art.